The present invention relates to a semiconductor device, particularly to, a semiconductor device such as a read only memory (ROM), a random access memory having dynamic circuits (DRAM) and the like, in which internal circuits have both states of active/precharge.
A semiconductor device generally has a circuitry in which an external signal state can be transmitted into internal circuits thereof even in cases when and after a power source is turned on. In both cases, it is too difficult to initialize inside of the semiconductor device such as internal flipflop circuits and the other internal nodes by both states of active/precharge of external signals when the power is turned on. Actually, since it is incorrect to initialize the flipflops and internal nodes by input level of the external signals in the semiconductor device when the power is turned on, each circuit of a plurality of the internal circuit blocks possesses both active/precharge states, thereby resulting an occurrence of an abnormal current or the like. Furthermore, in a nonvolatile semiconductor device which can electrically write data, when users input, at turning on the power, signal levels except allowed external signals at turning on the power, a writing error causes data in the memory to be destroyed.
Accordingly, in the conventional DRAM, several dummy cycles are supplied to the internal flipflops and nodes in the semiconductor device to be initialized. Furthermore, in the nonvolatile semiconductor device enabling an electrical writing such as a flash memory, an input level state is prescribed with respect to the external signals when the power is turned on, in order to prevent the writing error at turning on the power. This is one of the reasons why it is difficult to use the nonvolatile device such as the flash memory.
As described above, in the conventional semiconductor device, it is the problem that the simultaneous condition of the active state and precharge state in each internal circuit causes the semiconductor device to have erroneous operation such as an occurrence of an abnormal current corresponding to the state of the external signal.